DynamoDB On-Demand Capacity Mode

• There are two Read/Write capacity modes for DynamoDB: On-demand and Provisioned.

On-Demand Mode

• It is fully-managed and flexible.
• Throughput is automatically adjusted based on workload needs.
• Throughput scaling is handled automatically.
• Pay only for the actual reads and writes performed.
• On-Demand mode eliminates the need to predefine or manage throughput capacity.
• Throttling will not occur unless service limits are exceeded.
• It is designed to accommodate sudden and unpredictable traffic spikes.
• On-demand mode supports multi-region replication and real-time data change capture through streams.
• It is ideal for apps with variable traffic avoiding over-provisioning or underutilizing resources.
• Both strongly consistent and eventually consistent reads are supported.

When to Use DynamoDB On-Demand Mode:

• Suited for applications with sudden or highly variable traffic patterns, such as mobile apps, web apps, or services that experience fluctuating demands.
• This mode is a cost-effective option for startups and new applications where traffic patterns are unknown, enabling DynamoDB to automatically handle scaling.
• On-demand mode can be used for development or testing environments.
• Used for handling seasonal traffic spikes where manual scaling would be difficult

Provisioned Mode

• Read and write capacity units (RCUs and WCUs) are specified.
• Capacity-based billing is implemented.
• Guaranteed throughput is provided within provisioned limits.
• Requests are throttled if provisioned capacity is exceeded.
• Auto Scaling is an optional feature.
• Burst capacity allows for handling traffic spikes.
• It offers predictable read and write performance with capacity planning.
• Continuous backups and point-in-time recovery are supported.
• Change capture and real-time processing are enabled.
• Multi-region replication with independent provisioning is available in each region.
• Support for ACID transactions is included, which incurs additional throughput cost.

When to Use Provisioned Mode:

• For workloads with predictable and steady throughput requirements such as stable, high-traffic apps.
• In scenarios where cost control is a priority and throughput requirements are known in advance.
• This mode is appropriate when DynamoDB is required to adjust throughput dynamically based on demand through Auto Scaling.

Features

• Reserved capacity is a billing option for stable, predictable workloads over long periods.
• Reserved capacity is a long-term commitment to specific RCUs and WCUs for 1 to 3 years.
• Discounted pricing is offered for reserved capacity.
• Auto scaling dynamically adjusts throughput based on utilization.
• Auto scaling lowers costs by matching capacity to demand.
• Set up complexity involves requires setting minimum, maximum and target utilization levels.
• Minor delays in scaling might occur, but it's designed to be responsive.
• Throughput refers to the rate at which data can be processed or transferred within a specific service or system, measured by the number of operations (reads, writes, requests, etc.) handled over a given period.

DynamoDB offers On-Demand capacity mode, a fully-managed, flexible option that automatically adjusts throughput based on workload needs. You only pay for actual reads and writes, eliminating the need for pre-defining capacity. It is suitable for variable traffic and supports multi-region replication.